Added the /html command
Added the /html command

This command lets you send html messages through riot. This is
incredibly useful for doing advanced formatting not supported by
markdown and lets riot support even more html tags.

Signed-off-by: Waylon Cude <804802544ff3938bdcf33bb813c0f32163fc576e@finzdani.net>

matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk